Japanese Laid-Open Patent Publication No. 2002-329530 discloses a sheet-type battery with the objects of both miniaturization of a battery and increased capacitance through effective use of a separator or solid electrolyte layer and effective use of the internal space of a battery. Such sheet-type battery is characterized by having a plurality of anode sheets and a plurality of cathode sheets stacked so as to be alternately disposed with a separator in between and the separator being formed of a continuous sheet that is folded into a zigzag so as to be threaded between adjacent anode sheets and cathode sheets.